Breast cancer hormone therapy side effects

• A quick guide to what's on this page
• What side effects are
• Why you get side effects
• General side effects of hormone therapy
• Possible longer term side effects
• Where to find more information

Side effects are the unwanted effects of treatment. Hormone therapy for breast cancer affects people differently. Some people have more side effects than others. And unfortunately it is something we can’t predict before you start treatment. You may find that you have one side effect but not another. Many women find that the side effects are often worse at the start of treatment. They usually settle down after a few weeks or months.

Side effects may sometimes have positive effects for some women. A Cancer Research UK study in 2008 looked at hormonal therapy side effects in women taking tamoxifen or anastrozole. Women who had effects such as hot flushes, night sweats and painful joints within three months of starting treatment were 10% less likely to have a recurrence of breast cancer, compared to women who did not have side effects.

Hormones occur naturally in the body and control the growth and activity of cells. We know that the female hormones, oestrogen and progesterone, affect the growth of some breast cancer cells. Hormone therapy works by

• Reducing the amount of particular hormones in your body
• Blocking the effects of particular hormones

You get side effects because

• Your levels of some hormones are lower
• The treatment changes your body’s ability to use these hormones

The side effects you have will depend on the type of hormone treatment and the specific drug that you have. You can find detailed information about the side effects of individual hormone therapies by following these links

• Anastrozole (Arimidex)
• Letrozole (Femara)
• Exemestane (Aromasin)
• Tamoxifen (Novaldex)
• Goserelin (Zoladex)

There are some side effects that are common to most of the hormone therapies used to treat breast cancer. These include

• Hot flushes and sweats
• Change to your periods
• Less interest in sex
• Vaginal dryness or discharge
• Feeling sick
• Painful joints
• Mood changes
• Tiredness

Hot flushes and sweats

These can be difficult to cope with. Hot flushes are one of the most common symptoms women have when going through the menopause. You get hot flushes and sweats because you have lower levels of oestrogen.

All the hormone therapies used for breast cancer cause hot flushes. They are particularly common with pituitary down regulators because these drugs stop the body making any oestrogen. Just under half of women who take tamoxifen have hot flushes. Fewer women have hot flushes with the aromatase inhibitors.

Hot flushes usually reduce with time for most women. But some women find they continue during treatment. You may find that certain things, such as tea and coffee or spicy food, trigger them and that it helps to cut down on these.

Doctors sometimes prescribe drug treatment to control symptoms. They may try a drug called clonidine or antidepressants such as paroxetine.  You won't be offered antidepressants if you are taking tamoxifen.  This is because the antidepressant can stop the tamoxifen from working as well as it should. We have information about dealing with sweating in our section on coping physically with cancer.

Changes to your periods

If you have gone through your menopause this won’t affect you. If you are taking tamoxifen your periods may become lighter and irregular or they may stop completely.

If you are taking a pituitary down regulator your periods will stop completely. They might start again - usually within 6 to 12 months of your treatment stopping. But for some women they don’t start again, and they have an early menopause. This is more likely if you are near the age of your natural menopause.

Less interest in sex

Many factors can lower your interest in sex when you have cancer, including hormone treatments. In women the adrenal glands make small amounts of the hormone androgen, which affects sex drive. A lower level of androgen reduces your interest in sex. Other factors that can affect sex drive include vaginal dryness, tiredness, mood changes, worry and loss of confidence.

Once treatment has finished your sex drive usually goes back to how it was before treatment. Most women take hormone treatment for at least 2 to 5 years. The impact it has on your sex drive sometimes becomes less over time, as you adjust to the treatment. It can help to take your time and not rush things. Think about why you feel less like sex. Are you tired? Could you get more rest? How do you feel about how you look and how others see you? Has your confidence been knocked - are there things that you can do to boost it? Try to be open and talk to your partner about how you are feeling.

Although it can be difficult, just talking about it to someone else may help. As well as your partner, you could try talking to a close friend, your doctor or nurse. If you are feeling low, counselling may help. Your doctor may be able to give you treatment for tiredness or depression, if that’s right for you.

There is more information about coping with being less interested in sex in our sex, sexuality and cancer section.

Vaginal dryness or discharge

This is an uncomfortable and sometimes painful side effect of hormone treatment. Dryness can make you more likely to get vaginal infections. And it can also put you off having sex. Vaginal discharge is more common with tamoxifen than with the other types of hormone treatment.

There are a number of different creams and gels you can use to help vaginal dryness. Talk to your doctor about what you can use. An oestrogen cream might be possible (the amount of oestrogen in the cream is very small). There is more information about managing vaginal dryness in the sex and cancer section.

Feeling sick

This side effect is often worse for the first few days of taking hormone treatment and settles down quickly. If you are taking tablets it might help to take them after you have eaten. If you feel very sick, and can't eat and drink, talk to your doctor. You may be able to have anti-sickness tablets.

Painful joints

This is a particular problem with aromatase inhibitors and pituitary down regulators, although any of the hormone treatments may cause painful joints. You can take a mild pain killer such as paracetamol or ibuprofen. If the pain continues, tell your doctor.

Mood changes

Mood changes are a common side effect of hormone treatment. Coping with them can be difficult - not just for you but also for your family and friends. You may find that you have mood swings, or that you feel low. Many women find that these mood changes improve with time but talk to your doctor or nurse if they carry on.

There is more information about feeling low in the section on coping physically with cancer of CancerHelp UK.

Tiredness

Feelings of tiredness and fatigue are common when having hormone treatments. Coping with this side effect be difficult and frustrating. Again, your energy levels may improve with time although you may find you have some tiredness for the whole time you are having the treatment.

You can find more information about managing fatigue in the section on coping physically with cancer of CancerHelp UK.

There are a few longer term side effects of hormone treatments. These are rarer and include

• Bone thinning
• Womb cancer
• Eyesight changes

Bone thinning

Any drugs that block your body from making oestrogen can make you more prone to bone thinning or osteoporosis. Bone thinning can increase your chance of breaking a bone.

Bone thinning is a particular problem with taking aromatase inhibitors for a long time. Before you start treatment, you should have a ' DEXA scan' to check the strength of your bones (bone density). Your doctor may recommend that you don’t have aromatase inhibitors if you already have some osteoporosis.

If you are taking an aromatase inhibitor drug your doctor may also give you calcium and vitamin D supplements to help lessen the effect on your bones. Exercise can help lower your risk of developing bone problems but it needs to be weight bearing exercise, such as walking, running or gym work. You can find more detailed information about osteoporosis risk and hormone therapy in our breast cancer questions section.

If you are taking tamoxifen, and have had your menopause, there is research to show that you are less likely to have bone problems than women who haven’t had tamoxifen. Tamoxifen can help to maintain bone strength. So it may help to prevent bone problems while you are having treatment.

Womb cancer

If you are taking tamoxifen, there is a very small risk of developing cancer of the womb. If you have any abnormal bleeding you should see your doctor and get your symptoms checked. The type of womb cancer caused by tamoxifen is nearly always curable and less of a risk to you than the breast cancer.

The other hormone treatments used for breast cancer do not increase your risk of womb cancer.

You can find more information about womb cancer on CancerHelp UK.

Eyesight changes

Tamoxifen can cause eyesight changes but this is very rare. If you notice any changes in vision, tell your doctor. You may need to have an eye check up.

Our breast cancer questions section has information about results of aromatase inhibitor trials, which you may find useful to read

• ATAC: anastrozole and early breast cancer
• Tamoxifen and exemestane trial